Anonymous tipsters have more credibility under a closely divided Supreme Court decision Tuesday that upheld the tip-incited search of a California man’s truck.

In a case that atypically split the justices, the court’s 5-4 majority concluded California Highway Patrol officers acted reasonably when they stopped and searched the truck after hearing about a reckless driver. During the August 2008 search in Mendocino County, the officers found 30 pounds of marijuana.

“We have firmly rejected the argument that reasonable cause for an investigative stop can only be based on the officer’s personal observation, rather than on information supplied by another person,” Justice Clarence Thomas wrote for the majority.

Liberal Justice Stephen Breyer joined three court conservatives in the decision.

But conservative Justice Antonin Scalia, who often allies himself with Thomas, joined three liberal dissenters in challenging the decision.

“Drunken driving is a serious matter, but so is the loss of our freedom to come and go as we please without police interference,” Scalia wrote. “To prevent and detect murder we do not allow searches without probable cause or targeted . . . stops without reasonable suspicion. We should not do so for drunken driving either.”

The case arose the afternoon of Aug. 23, 2008, when emergency dispatchers received a call that a silver Ford 150 truck had run another car off of coast-straddling Highway 1. The call included a description of the truck as well as its license plate number.

The responding California Highway Patrol officers, though, did not see any sign of erratic driving before they pulled over driver Lorenzo Prado Navarette and his brother, Jose Prado Navarette, several miles from the town of Fort Bragg. As the two officers approached the truck, they smelled marijuana. A search of the truck bed revealed four bags.

The court’s majority reasoned that the “indicia of reliability,” including the anonymous caller’s details about the truck, were sufficient to provide police with reasonable suspicion.

“The officer was therefore justified in proceeding from the premise that the truck had, in fact, caused the caller’s car to be dangerously diverted from the highway,” Thomas wrote. “Running another vehicle off the road suggests lane positioning problems, decreased vigilance, impaired judgment, or some combination of those recognized drunk driving cues.”

Paul Kleven, the Berkeley, Calif.-based attorney who argued on Navarette’s behalf, noted Tuesday that the decision potentially “has bearing” on cases that go beyond the kind of reckless driving allegations that instigated the 2008 search in Mendocino County.

“I’m sorry the court went that way,” Kleven said.

Anonymous tips have caused problems in past Supreme Court cases.

In a 2000 case out of Florida, the justices unanimously ruled that Miami-Dade Police Department officers were wrong to search a teenager at a bus stop based solely on an anonymous tip that he was carrying a gun. Justices noted in the Florida case that police could not confirm the informant’s reliability.

Corroboration usually must accompany anonymous tips, courts have previously said.

“The California Highway Patrol in this case knew nothing about the tipster on whose word, and that alone, they seized Lorenzo and Jose Prado Navarette,” Scalia wrote. “They did not know her name. They did not know her phone number or address. They did not even know where she called from.”